Wireless communication systems are growing in size and number and are attracting ever larger numbers of subscribers for innovative communication services. The rise in the number of subscribers is welcomed and is much sought by respective wireless communication systems. Yet, an increase in the number of subscribers presents problems in maintaining a consistent level of quality communication services at low cost.
One service field particularly affected by an increase in the number of subscribers is the procedure used to locate wireless communication units operating within the service area of the system. A wireless communication unit must be located in order to deliver a call or message to the unit. The difficulty in locating a unit stems from one of the chief advantages of a wireless communication unit. The unit may be anywhere within or without the service area of the system.
One method used to locate a wireless communication unit is the North American cellular system, which is used generally by the cellular telephone systems operating in North America. Pursuant to the North American system, the wireless communication system receives periodic identification information (referred to as registration) from a unit operating within the service area. Registration provides the system with an indication that the unit is active and the relative cellular location of the unit. However, registration does not provide the wireless communication system with information regarding the prospective movement of the unit within or without the service area. To locate a unit pursuant to the North American system, the wireless communication system pages the last known cellular location of the unit. If the unit does not respond to the page at the last known location, the system pages for the unit in other cells of the system until the unit responds or until the system is satisfied that the unit cannot be found.
The North American system of locating a wireless communication unit is hindered by its general lack of information with respect to the movement and location of the unit. This lack of information greatly increases the number of pages that the wireless communication system must send and the number of cells that the system must check for the sought-after unit. This lack of information also prohibits the development of subscriber movement profiles and other useful methods which would increase the efficiency of the system in locating the wireless communication unit of a particular subscriber.
Another problem with the system-wide paging approach is its so-called "system overhead". System-wide paging consumes an inordinate amount of network resources in locating a wireless communication unit. Each page made in every cell of the service area increases the amount of radio signaling channel airtime required to locate the wireless communication unit so that a telephone call or message can be completed. An increase in the amount of channel airtime required to locate a wireless communication unit reduces the amount of channel airtime available to complete other calls and messages, and thus reduces the effective capacity of the overall wireless communication system. Time is lost and calls are delayed by paging for a wireless communication unit throughout an entire service area. Delayed calls discourage people from using wireless communication services. The discouragement, in turn, negatively affects wireless communication service revenue. System-wide paging also consumes infrastructure signaling and switching system computing resources.
Wireless communication systems using the North American system provide for automatic registration of the location of a wireless communication unit when the unit is first turned on or when the unit first enters the service area of a foreign wireless communication system. A "foreign" system is defined herein as a wireless communication system other than the system from which service is subscribed by the subscriber using the wireless communication unit. A unit operating in the service area of a foreign system is referred to as a roamer. Automatic registration procedures generally do not track or locate a wireless communication unit after its initial registration with the system. Thus, if a wireless communication unit does not respond to a page made to its location of initial registration, the unit must be paged in each of the cells of the service area until it is found or until the system is satisfied that the unit cannot be found.
Yet another problem with North American system-wide paging is that a wireless communication unit located outside its "home" wireless communication service area (a "roamer") will not receive or "hear" the page broadcast within its own service area. Generally, a roamer is not paged in the foreign wireless communication area unless certain conditions have been satisfied. The first condition is that the subscriber must have registered the presence of the wireless communication unit with the foreign wireless communication system. This condition may be satisfied by a feature available in certain wireless communication systems known as autonomous registration. This feature allows a roamer to register automatically when entering another system. The second condition that must be satisfied is that the home system must know the whereabouts of the roaming subscriber. In some wireless communication systems, this second condition is satisfied by an information exchange between the home and foreign systems. By this exchange, the foreign system provides the home system with information regarding the forwarding of calls to the subscriber roaming in the foreign system's service area. There are established procedures for paging the subscriber through the facilities of the foreign wireless communication service if these conditions are satisfied. However, a roaming subscriber, especially one on the border of the home service area, may traverse the home system/foreign system border numerous times in a single day. Each entry into a different service area requires a new registration. A subscriber thus may quickly tire of re-registering, or may not be aware of the need to re-register.
Another method used to locate a wireless communication unit is the Global System Mobile ("GSM") system, which is used generally by the digital cellular systems operating or scheduled to be deployed in Europe, Australia, New Zealand and in parts of the Orient. In sum, the GSM system keeps track of wireless communication units within the service area by requiring each wireless communication unit to register its location every time the unit moves into a different division of the service area. The geographic area served by a wireless communication system using the GSM system is divided into geographic areas referred to as mobile switching center (MSC) location areas, which in turn are subdivided into cells. Each of the MSC location areas, as well as each of the cells, is assigned a unique identification number. The identification numbers are broadcast periodically over the signaling channels of the respective geographic division of the wireless communication service area.
In operation, each wireless communication unit monitors the strongest signaling channel of the geographic division wherein the unit is located. In particular, the wireless communication unit monitors the signaling channel for the MSC identification number and for telephone call and message signals directed to the unit. When a wireless communication unit enters a new geographic division of a wireless communication system using the GSM system, the unit notes the new identification number broadcast over the division's signaling channels. In response to the new identification number, the unit registers its presence within the division. In this manner, the location of any particular wireless communication unit within the service area is known.
There are several disadvantages to the operation of the GSM system in locating wireless communication units within a service area. One of the principal disadvantages is that the geographic segmentation of the service area into MSC location areas and cells is relatively fixed. Changing the geographic segmentation arrangement is difficult. Yet, finding an optimum formula for the geographic segmentation of a wireless communication service area is problematic. For example, the requirements of the subscribers within the area may change with time, thereby affecting the optimum size of any particular geographic segment of the service area. Sizing geographic divisions too small results in an unnecessary amount of registrations by wireless communication units entering a particular division. Too many registrations unnecessarily burden the wireless communication system infrastructure and block or delay the completion of telephone calls or messages.
It is possible to program a unit to automatically register after a predetermined amount of time has passed since its last registration or subscriber communication. However, with an automatic registration system, frequent wireless communication unit registrations increase the transmit time of the units, thereby draining the energy source of portable or self-contained units. This depletion of the energy source cuts into the amount of time available for the subscriber to place telephone calls, deliver messages or receive same. This negatively affects wireless communication service revenue because it reduces the amount of time that a subscriber has available for placing or receiving calls or messages.
If the wireless communication service area is divided into too few geographic divisions, the GSM system encounters some of the same disadvantages of the North American system. Too few divisions within a wireless communication service area can delay or block telephone calls or messages because the particular unit has to be paged in each of the many cells of the service area. This unnecessary paging consumes signaling channel air time, thereby delaying and blocking other calls.
As a result of the use of fixed geographic divisions, the GSM system loses flexibility in accommodating different types of subscribers and in developing subscriber profiles. For example, under the GSM system, a subscriber who travels the same way to work each day through three geographic divisions of a wireless communication service area using the GSM system has to register the wireless communication unit in each of the three divisions traversed. On the way home, the subscriber registers the wireless communication unit with the same three divisions, but in reverse order. These five or six registrations take place every workday, even if the subscriber's pattern of travel never varies.
As noted, the popularity of wireless communication service continues to increase, and the implementation of more wireless communication systems is planned. Continued development of wireless communication service includes plans for greater numbers of wireless communication units, greater numbers of divisions within a wireless communication service area and smaller sized divisions. The increases in the number of wireless communication units and cells, together with the reduction in the average size of the divisions, exacerbate the problems described above in connection with the location and tracking of a particular wireless communication unit within the service area.
Continued development of wireless communication service also includes plans for reduction in the physical size of wireless communication units. Although smaller wireless communication units may be easier to handle and more versatile in terms of storage space, a smaller wireless communication unit reduces the amount of space within the wireless communication unit dedicated to the battery or other energy source, thereby limiting the available talk time and standby or listen time before recharging or replacing the battery. Thus, a small wireless communication unit has only a limited capacity to make and receive telephone calls or messages. This limited capacity is quickly consumed if the wireless communication unit is required to frequently register its location with the wireless communication system, or to frequently acknowledge pages from the wireless communication system.
Accordingly, there is a need for a wireless communication management system that can locate a wireless communication unit without paging for the unit throughout the entire service area, and that allows for the minimization of the number of times a unit is required to register its location with the wireless communication system.